“They were punching at people walking either side of the road,” he said. “One man was being kicked as he lay on the floor. The people were terrified, they weren’t fighting back.”

In the midst of the fighting, the two attackers took water bottles from their car and began squirting people with them.

“My first thought was ‘why are they squirting water’ but then I realised it was acid,” the witness said.

“People were screaming in pain and running. I heard one person shouting he couldn’t see and saying ‘it’s in my eyes’.”

Scotland Yard is not treating the attack as a hate crime. However, Detective Sergeant Quinn Cutler described the incident as ‘vicious and unpleasant’, and a number of people had been left with lasting injuries.